namespace LeftRightMid
{
    /// 
    /// Summary description for Class1.
    /// 
    class LeftRightMid
    {
        /// 
        /// The main entry point for the application.
        /// 
        [STAThread]
        static void Main(string[] args)
        {
            
            //assign a value to our string
            string myString = "This is a string";
            //get 4 characters starting from the left
            Console.WriteLine(Left(myString,4));
            //get 6 characters starting from the right
            Console.WriteLine(Right(myString,6));
            //get 4 characters starting at index 5 of the string
            Console.WriteLine(Mid(myString,5,4));
            //get the characters from index 5 up to the end of the string
            Console.WriteLine(Mid(myString,5));
            //display the result to the screen
            Console.ReadLine();
        }

        public static string Left(string param, int length)
        {
            //we start at 0 since we want to get the characters starting from the
            //left and with the specified lenght and assign it to a variable
            string result = param.Substring(0, length);
            //return the result of the operation
            return result;
        } 
        public static string Right(string param, int length)
        {
            //start at the index based on the lenght of the sting minus
            //the specified lenght and assign it a variable
            string result = param.Substring(param.Length - length, length);
            //return the result of the operation
            return result;
        }

        public static string Mid(string param,int startIndex, int length)
        {
            //start at the specified index in the string ang get N number of
            //characters depending on the lenght and assign it to a variable
            string result = param.Substring(startIndex, length);
            //return the result of the operation
            return result;
        }

        public static string Mid(string param,int startIndex)
        {
            //start at the specified index and return all characters after it
            //and assign it to a variable
            string result = param.Substring(startIndex);
            //return the result of the operation
            return result;
        }

    }
}

Left, Right and Mid functions in C#

c

C#